In the present proposal an indirect effect of oncogenic agents in leukemogenesis is hypothesized. It is possible that carcinogens cause alterations in the proper maturation and differentiation of T cells, resulting in an imbalance in the immune system which then leads to malignancy. It is assumed that any defect is subtle. Therefore, it is proposed to use more refined immunological techniques to study the normal maturation and differentiation of T cells. Allogeneic effect factor (AEF), which has been shown to have a profound effect on the differentiation of B cells, will be used as a probe for study of differentiation of pluripotential bone marrow stem cells into the lymphoid line. Basic understanding of stem cell commitment to T cell development will allow study of anomalies leading to malignancy.